This invention will be described as applied to the measurement the carbon dioxide (CO.sub.2). Such measurement apparatus is generally referred to as a gas analyzer and will be described as a carbon dioxide analyzer. The non-dispersive infrared technique utilizing the 4.26 microns absorption band of CO.sub.2 has been widely used in the gas analyzer industry for the detection of this gas. The term "non-dispersive" refers to the use of spectral band-pass filtering. This technique offers a number of advantages including speed of response and greater sensitivity over older methods that used the principle of heat transfer based upon radiation absorption by CO.sub.2. However, this non-dispersive infrared technique is not immune to instrument zero and span drifts due to changes incomponent characteristics caused by either aging or externally induced stimuli. Furthermore, this method does not automatically exploit the other implicit advantages of this technique in achieving instrument stability, interference rejection by other absorbing gases, and ease of recalibration.